In a medium saucepan, combine cranberries, granulated sugar, and water. Bring to a boil over medium heat, cook for 5-10 minutes until thickened and cranberries burst. Cool for 20 minutes.

Preheat oven to 375°F (190°C). Line an 8x8-inch pan with parchment paper.

Cream together softened butter and brown sugar until fluffy, about 2-3 minutes. Mix in extract, then gradually add flour, cornstarch, and salt until combined.

Press ⅔ of the shortbread dough into the bottom of the pan. Spread cooled cranberry filling evenly over it. Crumble remaining dough over filling.

Bake for about 30 minutes, or until golden brown. Let cool completely in the pan.

Use parchment to lift the bars from the pan. Slice into bars or squares and cool completely before serving.